With the advent of high speed aircraft with its advanced type of engines, in order to enhance the high cycle fatigue life of component parts, particularly the turbine rotor blades, it has become necessary to incorporate damping techniques so as to reduce vibratory stresses occasioned by the higher speeds. For turbine rotors that utilize fir tree attachments to secure the blades to the disk, such dampers have been incorporated in the space between blades at the blade root/disk attachment sections. Examples of dampers of this sort are disclosed in U.S. Pat. Nos. 4,182,598 entitled "Turbine Blade Damper" granted to C. J. Nelson on Jan. 8, 1980, 4,101,245 entitled "Interblade Damper and Seal for Turbomachinery Rotor" granted to J. R. Hess and H. F. Asplund on July 18, 1978, 4,455,122 entitled "Blade to Blade Vibration Damper" granted to R. A. Schwarzmann and H. J. Lillibridge on June 19, 1984, and 3,887,298 entitled "Apparatus for Sealing Turbine Blade Damper Cavities" granted to J. R. Hess and J. R. Kozlin on June 3, 1975, all of which are assigned to United Technologies Corporation, the assignee of this patent application.
While those embodiments exemplified in the above noted patents disclose means for achieving damping, they all to some extent require complex means of assembly and disassembly necessitating the removal of more than one blade to replace another blade or component in the disk/blade assembly, or to install a blade, damper and/or seal.
We have found that we can provide an improved retention system for the turbine rotor components by incorporating a unique rim configuration that employs snap rings to secure the blades in the disk. To this end, rearward retention of the blades is by a snap ring supported by hooks integral to the rear of the disk, and forward blade retention is by an inverted snap ring supported by a lug integral to the front of the disk lug. In this configuration the axial retention of the blades is provided by this snap ring and not the TOBI (Tangential On Board Injector) rotor seal which has been the common heretofore practice. To have designed the system incorporating heretofore design practices would have added an intolerable amount of weight to be capable of absorbing these axial loads. Among the advantages afforded by this inverted snap ring are:
(1) improved producibility of the snap ring groove, PA0 (2) lighter weight than heretofore known retention systems, and PA0 (3) full ring support for the snap ring for improved durability, leakage control and life.
This invention also contemplates an easily accessible damper and interstage platform seal which facilitates the assembly and disassembly of those components without the necessity of removing more than one blade. Hence, individual blades can be installed and removed without disrupting the rotor or changing the dynamics of the rotor. By virtue of this invention, a significant improvement in turbine maintainability and assembly is evidenced coupled with a reduction in tooling requirements and a less complex rim assembly.